Effects: a plug-in before a fill's or stroke's own 3D effect is told its fill or stroke

A 3D effect on a fill or stroke worked on copies of the object's fills
and strokes, and the copies were looked up among the object's items by
identity, so a live-effect plug-in before that 3D effect was given
`_context.item` "object" and a deferred stage there was listed with no
item. The drawn art, the 3D meshes and Expand as Wireframes now pass the
original item, so the plug-in is given `{"fill": i}` or `{"stroke": i}`
as docs/plugins.md describes. The paints of a type's first run still have
no item.

docs/target-app-parity.md

@@ -1873,6 +1873,7 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
 
 - **Plug-in parameters as their manifest presents them (G17):** each parameter may have a `label`, a `unit` shown after its value, `help` on its label and a `helpUrl` page opened from a button, a `group` (sections that fold, after the parameters outside any group) and a `visibleWhen` that shows it only while the checkboxes and choices it names have one of the listed values (a hidden parameter still goes to the plug-in). `string` and `numberList` parameters join number, int, bool and choice, and a plug-in declares up to 256 parameters, at most 64 outside groups. The filter, live-effect and exporter dialogs use these keys, and the Appearance panel's effect editor the labels, units, help and conditions; hosts from before them ignore them. Regressions: `crates/plugins/src/dialog.rs`, `crates/plugins/src/manifest.rs`, `crates/ui-egui/src/dialogs/tests_plugin_fields.rs`, `crates/ui-egui/src/panels/appearance.rs`. Scores and hours unchanged.
 - **Live-effect plug-ins read their object's paints (G17):** a live effect is given the object's `fills` and `strokes` as a filter gets them, read only, and `_context.item` (`"object"`, or the fill or stroke whose own effects hold it); the result is cached by paint too, so a change of paint runs it again. Regressions: `crates/engine/src/tests/plugins.rs`, `crates/plugins/src/effect.rs`. Scores and hours unchanged.
+- **Live-effect plug-ins before a fill's or stroke's own 3D effect:** a live effect listed before a fill's or stroke's own Extrude & Bevel, Inflate or Rotate effect is given `_context.item` for that fill or stroke (`{"fill": i}` or `{"stroke": i}`), not `"object"`, in the drawn art, in the 3D meshes and in Expand as Wireframes; a deferred stage there is listed at that fill's or stroke's place. Regressions: `crates/effects/src/tests/solidcontext.rs`. Scores and hours unchanged.
 - **Filter plug-ins set effects and stroke styles (G17):** a filter is given each object's effect records and its strokes' `join`, `cap` and `miterLimit`, and may return them; the records are admitted as `effect.apply` admits them (a known effect or installed live-effect plug-in, parameters it takes, one 3D effect that fits, no texture read from a file), and one refused refuses the output. Regressions: `crates/engine/src/tests/plugins.rs`, `crates/plugins/src/objects/tests.rs`. Scores and hours unchanged.
 - **Gradient stop plates from filter plug-ins are clamped (G17):** the four process `plates` of a gradient stop in a filter's or importer's output are clamped to 0–1, as its other colors are; a value that is not a number becomes 0, and an infinite one becomes 0 or 1 by its sign. Painted live effects still refuse such a stop. Regressions: `crates/plugins/src/objects/tests.rs`. Scores and hours unchanged.
 - **Plug-in data kept with the document (G17):** a filter writes JSON of at most 1 MiB with `documentData` (one undo step with its objects; `null` removes it) and reads it back in `_context.documentData`, which no other filter is given. It is the document's foreign data (`unknown.pluginData`, by plug-in id), as the perspective grid is, so the native file keeps it with no section of its own; an exporter is given the whole document, so it can read every plug-in's. Regressions: `crates/engine/src/tests/plugins.rs`, `crates/engine/tests/plugin_export.rs` (the exporter), `crates/doc/src/plugin_data.rs`, `crates/plugins/src/objects/tests.rs`. Scores and hours unchanged.